Screen encoder control with MSC

Is it possible to use a MIDI interface to control attribute encoders? have set up a MIDI controller (APC40) to expand the control surface of my M1, using Bome MTP to generate midi show control commands. I would like to assign the screen encoders in Onyx to encoders on the APC40 since the M1 does not have the physical encoders on the monitor. I know that this is possible with ShowCockpit, but while I think the software is great (!) I’m talking about a non-PC-driven setup in this case. I haven’t found any MSC documentation that addresses this application, and since I’m learning MIDI as I go I don’t even know if MSC is the right message format to accomplish this. Any help is appreciated, thank you.